Abstract A radical return to natural environments in public architecture is proposed. This requires a reasonably sophisticated understanding of building physics on the part of designers but there is a marked reluctance historically in the design community to acquire such expertise for fearing of destroying free artistic expression. This anti-scientific social practice may be the principle barrier to a sustainable future for the built world. The key to unravelling this prejudice may lie in understanding how modern perceptions of safe and comfortable environments evolved through early understanding of disease propogation through the air. The paper presents innovative later nineteenth century hospital designs as proto-modern buildings and suggests that aggressive mid-Twentieth Century advertising of air conditioning killed a highly productive stream of architectural design, overdue for vigorous re-examination to shift the prevailing 'will to form'.